Polymers based on aliphatic diols and in particular isosorbides are of great interest to the chemical industry. Isosorbides are derived from biologically based sources, namely sugars, rather than from the petroleum feed stocks used to prepare other structural units, or monomers. Isosorbide-based materials and products are biodegradable, have a low net environmental impact, and can be utilized as renewable resources by the plastic manufacturing industry. These materials and products can be used for the production of polymeric materials such as polycarbonates. Of particular interest are polymers based on isosorbides, such as 1,4:3,6-dianhydro-D-sorbitol; 2,6-dioxabicyclo[3.3.0]octan-4,8-diol; 1,4:3,6-dianhydro-D-glucitol; 2,3,3a,5,6a-hexahydrofuro[3,2-b]furan-3,6-diol, and isomers thereof.
Isosorbides are thermally unstable. As such, melt reactions conducted at above 220° C. can severely challenge the efficient production and commercial scale-up of isosorbide-based bisphenols via melt transesterification processes.
Accordingly, there is a need for efficiently producing isosorbide-based polymer structural units without sacrificing the commercial scale up capabilities of the production process. Such units can then be efficiently polymerized to form polymers that have desirable color properties (i.e. low yellowness) and acceptably high molecular weight for commercial application